title: Delineation of the postprostatectomy prostate bed using computed tomography: interobserver variability following the EORTC delineation guidelines.
abstract: OBJECTIVE
  The present study aims to assess the interobserver agreement of prostate bed delineation after radical prostatectomy using CT alone as proposed by the European Organization for Research and Treatment of Cancer (EORTC) guidelines.
  
  
  METHODS
  Six observers delineated the postoperative prostate bed (PB) and the original seminal vesicle position or remnants (SV) of 10 patients according to the EORTC guidelines. Contours were then compared for agreement between observers (the apparent volume overlap and generalized kappa statistics). Standard deviations were also calculated to measure the variability of the position of the outer margins.
  
  
  RESULTS
  The mean volume of 100% agreement (±1 standard deviation, SD) was only 5.0 (±3.3) ml for the PB and 0.9 (±1.5) ml for the SV, whereas the mean union of all contours (±1 SD) was 41.1 (±11.8) ml and 25.3 (±13.4) ml, respectively. The mean overall agreement corrected for chance was moderate for both the PB (mean kappa, 0.49; range, 0.35-0.62) and SV (mean kappa, 0.42; range, 0.22-0.59). The overall SD of the outer margins of the PB ranged from 4.6 to 7.0 mm
  
  
  CONCLUSIONS
  The delineation of the postprostatectomy bed using CT shows only a moderate observer agreement when following the EORTC guidelines.
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Ghent, Belgium. piet.ost@ugent.be
authors.forename: Piet
authors.initials: P
authors.lastname: Ost
authors.forename: Gert
authors.initials: G
authors.lastname: De Meerleer
authors.forename: Tom
authors.initials: T
authors.lastname: Vercauteren
authors.forename: Werner
authors.initials: W
authors.lastname: De Gersem
authors.forename: Liv
authors.initials: L
authors.lastname: Veldeman
authors.forename: Katrien
authors.initials: K
authors.lastname: Vandecasteele
authors.forename: Valérie
authors.initials: V
authors.lastname: Fonteyne
authors.forename: Geert
authors.initials: G
authors.lastname: Villeirs
mesh_terms: D019983:Guideline Adherence; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D015588:Observer Variation; D011184:Postoperative Period; D017410:Practice Guidelines as Topic; D011467:Prostate / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D012669:Seminal Vesicles / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden; D001743:Urinary Bladder / Q000000981:diagnostic imaging